When looking for specialty stickers, did you check your local copy/print-shop? They usually have a high-res color laser printer and sticker backings that would do just fine, for an acceptable price.
I haven't checked any local brick-and-mortar places. I didn't think I knew of any local copy/print shops, but one just came to mind. Thanks for the suggestion!
If you're willing to use stickers, why not just get some medium - to any - size labels, print what you want on them (including face/background color), and then trim them to size for the die face.
This is an option I have considered, but was hoping to not have the imprecision of cutting them out myself. If I could find some template stickers that were the right size/shape, it would be much preferable than having to cut them out myself. Another possible option would be to find a hole punch that would make it easier to punch out a sticker in the right size/shape.
Recently a company put out some dice with colored sides that you can remove and change -- designed to be useful for prototyping games:
Those look interesting, but still not quite right for what I want. I want the colors & designs on each face.
It's looking more and more like I'll be going the printing route.
Anyone know if 3D printers can do what I want? That would be cool.
EDIT: Looks like it's possible.
Sort of. But that one looks like it can only do 3 colors at once.I also found this
which shows off a printer capable of printing up to 390,000 colors, but that seems to be a site for buying the printer itself. Who knows if I could find a place that would let me make a custom order from them without buying the printer, or how much it would cost for such an order?